Copper alloys are used in many commercial applications. Many such applications involve the use of molds or casting to shape molten alloy into a rough form. This rough form may then be machined to the final form. Thus, the machinability of a copper alloy may be considered important. In addition, the other physical and mechanical properties such as ultimate tensile strength (“UTS”), yield strength (“YS”), percent elongation (“% E”), Brinell hardness (“BHN”), and modulus of elasticity (“MoE”) may be of varying degrees of importance depending on the ultimate application for the copper alloy.
One property imparted to copper alloys by copper is an antimicrobial effect. It is generally believed that alloys containing above 60% copper content will exhibit an antimicrobial effect. This antimicrobial effect appears to be through multiple pathways, making it very difficult for organisms to develop resistant strains. The antimicrobial effect of copper has been well studied, including recognition by the Environmental Protection Agency.
Copper alloys, particularly copper alloys having high levels of copper typically exhibit a copper-like color. This color may not be desirable in the end product, such as due to consumer preferences or compatibility with other materials used in the end product.
Further, although copper imparts many useful properties to copper-based alloys, copper (and high copper alloys) are susceptible to tarnish. Exposed copper or a copper alloy surface can discolor and develop a patina. This may provide an undesirable visual characteristic.
Attempts have been made at developing a “white brass” that provides the color of white/silvery metals while retaining the properties of a brass alloy. Copper Development Association Registration Number C99700, known in the industry as white Tombasil™, is a leaded brass alloy that provides a somewhat silvery color. However, C99700 presents many problems. First, it relies upon a relatively high lead content (˜2%) to maintain the desirable machinability, a content considered significantly too high for commercial or residential water usage. Further, the alloy is difficult to machine, difficult to pour, and the intended silvery color is susceptible to discoloration (blackening).
As a result of the tendency of copper alloys to tarnish, many consumer goods that are made from copper alloys are painted or plated to provide a more appealing color and to prevent the detrimental effects of tarnish. One such example is plumbing fixtures. However, the needs and desire to plate a copper alloy also prevents the copper alloy from providing its antimicrobial effect, due to the surface of the consumer good being of the plated material rather than the underlying copper alloy.